Calculate Initial Horizontal Velocity of Long Jumper

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The discussion focuses on calculating the initial horizontal and vertical velocities of a long jumper taking off at 8.25 m/s at an angle of 12.5 degrees. The initial horizontal velocity is calculated using the cosine function, while the vertical take-off velocity is derived using the sine function, resulting in 1.785 m/s. Participants clarify that the vertical component is indeed calculated with the sine of the angle, and there is confusion regarding the use of cosine for horizontal velocity. The conversation also touches on the jumper's height over time, noting that the vertical height will not remain constant after one second. The thread emphasizes the importance of understanding trigonometric functions in projectile motion calculations.
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A long jumper is able to take off with a velocity of 8.25m/s at 12.5dgs to the horizontal. Calculate:

a) the initial horizontal velocity
a) 8.25m/s

b) the vertical take off velocity
b) 8.25sin(12.5) = 1.785m/s, as far as i know Uxsin(theta) is the vertical velocity , except in the answer to the second half of the question it says it's 8.25cos(12.5) which is the equation to the horizontal velocity? anyone know why this is? thanks.
 
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Hi Sirsh! :smile:

(have a theta: θ and a degree: º :wink:)
Sirsh said:
A long jumper is able to take off with a velocity of 8.25m/s at 12.5dgs to the horizontal.
…
b) the vertical take off velocity
b) 8.25sin(12.5) = 1.785m/s, as far as i know Uxsin(theta) is the vertical velocity , except in the answer to the second half of the question it says it's 8.25cos(12.5) which is the equation to the horizontal velocity? anyone know why this is? thanks.

Well, it's definitely sin12.5º for the vertical component.

The book must be wrong. :redface:​
 
Hey tiny-tim, thanks for the signs :P does the verical component be8ing 1.785m/s mean that after one second the jumper will be 1.785m in the air ect until he hits max parabolic height then he'll decend until he hits the horizontal plain? thanks (:
 
Hey Sirsh! :smile:

It means he'll always be at the same height as if he'd jumped vertically with that speed. :wink:

But it won't be 1.785m after 1 second, it'll be 1/2 at2.
 
Oh okay, thanks alot! :D
 
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